1. Field of the Invention
The present invention relates to a radio telephone system.
2. Description of the Prior Art
The recent development in mobile radio communication systems, particularly in radio telephone systems, has been remarkable. In the radio telephone system, a user's mobile station is connected by radio to a base station which is connected to the fixed telephone network. As a method of communication between the base station and the mobile station, the multi-zone system has been available, wherein the base stations are dispersed to allow each of them to use the same frequency band so as to increase the total number of the mobile stations to be accommodated.
In this multi-zone system, each of the base stations is set to have a relatively small radio zone so as to cover the service area by a number of the base stations. This can reduce output levels of the respective base and mobile stations, while capable of increasing the number of the mobile stations to be accommodated.
Hereinbelow, a conventional radio telephone system will be described.
FIG. 9 is a block diagram showing a structure of the conventional radio telephone system.
In FIG. 9, numeral 1 denotes a base station connected to a wire circuit 3 and numeral 2 denotes a mobile station which is connectable to the base station 1 by radio. The mobile station 2 performs signal transmission and reception relative to the wire circuit 3 via the base station 1.
In the base station 1, numeral 4 denotes a communication section for receiving sound and data signals sent through the wire circuit 3 and for sending sound and data signals into the wire circuit 3. Numeral 5 denotes a B-M radio interface in the form of transmitter-receiver for call and control channels for communication with the mobile station 2. Numeral 6 denotes a base station antenna connected to the B-M radio interface 5. Numeral 7 denotes a base station ID storing section where an identification code of the base station for identifying classification, such as, service and owner company, of the base station is stored. Hereinafter, this identification code will be also referred to as “base station ID”. Numeral 8 denotes a mobile station ID storing section where an identification code/codes of the mobile station/stations 2 (hereinafter also referred to as “mobile station ID”) present in a radio zone of the base station 1 is/are registered. Numeral 9 denotes a location registration managing section for managing registration of the mobile station ID of the mobile station 2 present in the radio zone of the base station 1. Numeral 9a denotes a managing table where data of the mobile station/stations 2 present in the radio zone of the base station 1 is/are registered. Numeral 10 denotes a base station control section for controlling communications performed by the base station 1 relative to the mobile station 2 and a circuit control office and other operations of the base station 1.
On the other hand, in the mobile station 2, numeral 11 denotes an M-B radio interface in the form of transmitter-receiver for call and control channels for communication with the base station 1. Numeral 12 denotes a mobile station antenna connected to the M-B radio interface 11 for transmission and reception of radiowaves with the base station antenna 6. Numeral 13 denotes a base station ID storing section where a base station ID of a base station 1 having a classification which is connectable to the present mobile station 2 is stored. Numeral 14 denotes a mobile station ID storing section where the mobile station ID of the present mobile station 2 is stored. Numeral 15 denotes an operating section for performing dial inputting and instruction inputting, such as, “on-hook” and “off-hook”. Numeral 16 denotes a display section in the form of, such as, an LED (light-emitting diode) display or an LCD (liquid crystal display) for displaying information, such as, a dialed number and a date. Numeral 17 denotes a telephone transmitter and number 18 denotes a telephone receiver. Numeral 19 denotes a sound interface for receiving a sound signal from the M-B radio interface 11 for an output through the telephone receiver 18, for sending a sound signal from the telephone transmitter 17 to the M-B radio interface 11 and for performing signal gain adjustments in those instances. Numeral 20 denotes a mobile station control section for controlling operations of the mobile station 2.
Now, operations of the radio telephone system as structured above will be described hereinbelow.
First, the location registration of the mobile station 2 will be explained.
For specifying one of the radio zones of the base stations 1 where the mobile station 2 concerned is present, the location registration is performed to register the mobile station ID of the mobile station 2 in the base station 1.
The location registration is performed when a signal level received through the radio channel is lowered below a given value during communication and thus switching is necessary to another base station 1, or when an operation for the location registration is performed via the operating section 15 in the mobile station 2. On the other hand, there is another radio telephone system, wherein a location registration request is periodically transmitted from the mobile station 2 to cause the base station 1 to perform the location registration.
Hereinbelow, the location registration sequence will be described with reference to FIG. 10 which shows a location registration sequence diagram.
When the location registration becomes necessary due to the foregoing situation, the mobile station control section 20 causes the M-B radio interface 11 to transmit an location registration request signal and a mobile station ID via the mobile station antenna 12 (step 101).
When these signals are received at the B-M radio interface 5 of the base station 1 via the base station antenna 6, the base station control section 10 causes the B-M radio interface 5 to send a base station ID authentication request signal for requesting the mobile station 2 to transmit a base station ID stored in the mobile station 2 (step 102).
When the M-B radio interface 11 of the mobile station 2 receives this base station ID authentication request signal, the mobile station control section 20 reads out the base station ID from the base station ID storing section 13 and causes the M-B radio interface 11 to send a base station ID authentication response signal including the read-out base station ID (step 103).
When the B-M radio interface 5 of the base station 1 receives this authentication response signal, the base station control section 10 checks the base station ID included in the received authentication response signal with a base station ID stored in the base station ID storing section 7. When both identification codes are matched with each other, the base station control section 10 causes the mobile station ID storing section 8 to store the mobile station ID transmitted in advance from the mobile station 2. Simultaneously, the base station control section 10 sends this mobile station ID to the location registration managing section 9.
The location registration managing section 9 registers data of the mobile station 2 in the managing table 9a, and controls the communication section 4 to send a signal indicative of completion of the location registration of the mobile station 2 to a managing center (not shown) which is connected to the wire circuit 3 and performs the overall management of the base stations. Subsequently, the base station control section 10 transmits to the mobile station 2 via the B-M radio interface 5 a signal representing that the foregoing location registration processes have been acknowledged (step 104). Thereafter, the base station control section 10 further transmits to the mobile station 2 via the B-M radio interface 5 a signal requesting the mobile station 2 to disconnect the radio channel now used (step 105).
In response to this disconnect request signal, the mobile station 2 sends a signal indicative of disconnection of the radio channel to the base station 1 so as to release the current radio channel (step 106).
The location registration of the mobile station 2 is completed by the foregoing operation sequence.
Now, explanation will be made to a case where a call is made from the mobile station 2.
The mobile station control section 20 transmits the base station ID stored in the base station ID storing section 13 and other given signals, such as, a sound signal, via the M-B radio interface 11.
When the B-M radio interface 5 of the base station 1 receives these signals, the base station control section 10 compares the received base station ID with the station ID stored in the base station ID storing section 7. When both identification codes are matched with each other, the base station control section 10 connects between the B-M radio interface 5 and the communication section 4 to allow communication between the wire circuit 3 and the mobile station 2.
Now, explanation will be made to a case where the mobile station 2 receives a call.
When the communication section 4 of the base station 1 receives from the wire circuit 3 a reception request signal including date of the mobile station 2 to be called, the location registration managing section 9 checks whether the data of the mobile station 2 included in the received signal are registered in the managing table 9a. If registered, the location registration managing section 9 notifies the base station control section 10 accordingly. In response to this, the base station control section 10 causes the B-M radio interface 5 to transmit the corresponding mobile station ID stored in the mobile station ID storing section 8 and a sound signal. When the M-B radio interface 11 of the mobile station 2 receives the transmitted signal, the mobile station control section 20 compares the received mobile station ID with the mobile station ID stored in the mobile station ID storing section 14. When both identification codes are matched with each other, the mobile station control section 20 transmits a connection request signal via the M-B radio interface 11. When this connection request signal is received by the B-M radio interface 5 of the base station 1, the base station control section 10 connects between the mobile station 2 and the wire circuit 3.
In the foregoing conventional radio telephone system, however, in case the location registration is performed based on the operation of the operating section 15 of the mobile station 2, the data and the mobile station ID of the mobile station 2 continue to remain in the managing table 9a and the mobile station ID storing section 8 of the basic station 1 until a location registration of the mobile station 2 is performed in another radio zone. Accordingly, even when the mobile station 2 goes away from the radio zone of the basic station 1 concerned, the data and the mobile station ID of the mobile station 2 still remain in that base station 1. This requires the base station 1 to make a transmission for call reception to the mobile station 2 which is now outside the radio zone concerned. This further requires unnecessarily increased storage capacities of the mobile station ID storing section 8 and the managing table 9a. Particularly, in the base station 1 having a radio zone where the coming-in and coming-out of the mobile stations 2 are frequent, a great amount of data which are actually not necessary remains stored.
Further, in the foregoing conventional radio telephone system, the base station 1 always transmits radiowaves in the maximum output power so as to make it possible to communicate with the mobile station 2 anywhere in the radio zone concerned. Accordingly, even when no mobile station 2 is present in the radio zone concerned or the mobile stations 2 are concentrated around the base station 1, the radiowaves are transmitted in the maximum power. This consumes the electric power more than necessary.